The present embodiments relate to medical imaging of an implant. Metallic implants are used to replace degenerative joints or support disabled bones. For example, a physician implants a metallic component (i.e., an implant) in a patient undergoing knee arthroplasty. The implant replaces the patient's knee joint.
In many applications of implants, kinematics analysis of the abnormal joints or bones helps the success of the implant. To obtain the kinematics information, a three-dimensional (3D) model of the implant device is aligned with a sequence of X-ray images. The alignment provides accurate pose (e.g., orientation) estimates of the implant in the body, allowing the physician to monitor seating and performance of the implant. FIG. 1 shows a 3D model 36 of an implant. FIG. 2 shows an X-ray image 32 of the implant 30 relative to bone 34.
In one alignment approach, the model's 36 occluding contour is aligned with the x-ray silhouette in the two-dimensional x-ray image. Iterative closest point (ICP) is used to align the contour with the silhouette. ICP relies on accurate detection of edges of the silhouette in the x-ray image. However, ICP is not robust where outlier candidates exist. While relatively more absorbing of x-rays, identification of the implant in the x-ray image may be complicated due to bone or other x-ray absorptive objects.